The proposed studies will attempt to determine the role played by central noradrenergic systems in the morphine abstinence syndrome and the mechanism by which drugs like clonidine and related analogs can reverse or attenuate this syndrome. Neurophysiological and biochemical strategies will attempt to correlate biochemical changes observed in opiate addiction and their reversal by clonidine with functional changes in the activity of central noradrenergic systems. These studies in nonhuman primates will provide a critical bridge between single neuronal activity studies in rodents and clinical studies in humans. Findings from this research may be useful to clinical studies of clonidine in opioid dependent humans, and may add information regarding central functions of endogenous, medically useful, and abused opioids.